The Life and Death of the Planet Earth: How the New Science of Astrobiology Charts the Ultimate Fate

[22 January 2003]

By Wesley Burnett

BREATHTAKING!

“Time, A maniac scattering dust.” Tennyson

I visit my great grandfather’s grave in the Meadows of Dan and wonder what made his children leave this beautiful land at the foot of the Blue Ridge. Well, wait a minute. I’m assuming today’s world looks like yesterday’s. That ain’t necessarily so. Change is constant. I also muse that my great grandfather is a distant relative who lived more like Job than me. That makes me think of my great grandchildren who will live in a world, for better or worse, so different from mine we might as well live on different planets as in a different time. This little bit of change and this narrow slice of time I struggle with is as nothing compared to the dimensions geology and astronomy students must contemplate. But this is where Ward and Brownlee start their discussion of the life and death of the planet Earth—with change and incomprehensible quantities of time.

Finding planets beyond our solar system has led to speculation that Earth-like planets must be all over the universe. When we count all those stars and contemplate all that time, probability seems to favor many millions of Earth-like planets. Elsewhere, Ward and Brownlee have argued against this idea. Earth’s situation is so unusual that Earth-like planets must be awfully rare. Here they consider the unique events that have gone into building our planet. Time and lots of it. Just the right kinds of stuff coming together to form a solid planet just the right distance from the right kind of star that allows the right sort of stuff, water specifically, to condense without boiling away into the heavens or condensing into permanent ice oceans. An exceptionally large moon that mixes ocean water and land daily. Even land itself is something of a miracle—lightweight minerals boiled-up from the inside of a planet that is just hot enough that that happens without turning the place into a volcanic hell. How breathtaking.

Lifelike things, bacteria, started developing about as soon as Earth cooled enough for the molecules to find each other and stay together for at least awhile. By about 3 billion years ago stromatolites, mats of cooperating photosynthetic bacteria, filled the oceans and began producing oxygen. Oxygen spent much of its history rusting iron. That done, it could pass the eons preparing the atmosphere for land plants and their grazers. Life prepares itself for yet more life. That’s breathtaking too.

That must be evolution’s purpose, to create more species, more biological production, more life. That is what we have long wished to believe. But no, it isn’t so. The new science, astrobiology, tells us that maximum biological production was reached some 200 to 300 million years ago. Even in terms of species, a stasis has been reached. Species would come and go but the number would remain about the same even without human intervention. In E. O. Wilson’s terms, the island Earth is full-up. All this means we live on a planet that long ago reached maturity and is now well on its way to its inevitable decline and death.

So what of the future? Well, at the moment the planet has this little problem, us. We’re killing things, both species and total biological productivity, with gay abandon and that alone would lead to warming the planet. And then of course, there is all that nice, warming carbon dioxide we’re turning loose. So things will get hotter for a while but in a few centuries the few remaining humans will skulk back to the caves they came from and things will get back to ‘normal’. The ice will come and go. Evolution will go to work, but new species will always reflect the planet’s history of human occupation. Continental drift will get all the continents together again and that will heat things up but good. The planet will get warmer and warmer. Plants will go first, starved for carbon dioxide. Then the animals will use up the last atmospheric oxygen. Eventually only the bacteria will survive, and we’ll be back to where we started. And then nothing, until the planet is consumed finally in its expanding star.

A grim story with an unhappy ending, most of which is not of the slightest relevance to me. Heck, I’m still having a hard time grasping the idea of great grandfathers who aren’t really of much relevance to me either. But ecologists tell us that everything is tied to everything else. And there in lies the lesson. As one systems falls apart, the rest are weakened and that’s breathtaking.

I’m blessed to live on a maturing planet. While I can never stop cosmological events, I can take care of the planet, my home, and I’d better get on with it before it’s too late. Life is so unusual in this wilderness we call the universe that we might as well think of it as unique. It’s a precious gift, one to be valued.

One might wish greedy politicians contemplating their arsenals or ways to stimulate economic development at the most outrageous environmental costs would spend a little time with this book. Unfortunately, this probably won’t happen. It will be read, and loved, by those whose teacup is natural and environmental science. And while part of the purpose of this book is to explicate the new science of astrobiology, readers of Asimov’s science fiction will find much of it old hat, though blessed with a simplicity and order Asimov never achieved. What Ward and Brownlee have accomplished is awfully good science writing elegantly presented. It grasps and holds our attention and forces us to look at this thing we call nature, this little planet next to an obscure star on the edge of a galaxy like so many others, lost in a hostile wilderness, the universe, in entirely new ways. It’s a painful view but breathtaking, nonetheless.